TEMPERATURE-DEPENDENCE OF IMPACT DAMAGE I N A SI3N4 DISK BY A SPHERICAL-PARTICLE

A model experiment for examining impact damge dependence on temperatur e is conducted on Si3N4 for turbine use. A zirconia sphere is shot ont o a Si3N4 disk at RT and at 1200 degrees C, and then surface damage as well as internal damage is examined, The results indicate that a gene rated crack system changes from a Hertzian cone crack to a median crac k in accordance with the experimental temperature change. It is conclu ded that the hardness degradation at 1200 degrees C generated a change in the stress field from elastic to elastic/plastic, resulting from s oftening of grain boundary glassy phase.